Why is it important to align bones to view axis?
The operation is &quot;recalculate roll.&quot;  It can be accessed from the armature menu, via armature-&gt; bone roll-&gt; recalculate roll-&gt; whatever.
You don't necessarily have to align bones to the view axis specifically.  What you want to do, though, is make sure your bones have appropriate tilts.  Using the recalculate roll option to do so is the easiest way to control your tilt.  (I tend to recalculate to cursor myself.)
Why?  Think about a lower arm bone.  Your elbow rotates in a single axis, more or less, and if you animate a model where its lower arm rotates outside of this axis, it's going to look broken.  So you're either going to use angle limits, or transform locks, or IK angle limits, or expect the animator to animate in specific bone-local axes.  Doing any of these requires that you set the tilt such that the unlocked axis corresponds to the way you actually want the elbow to bend.
In the case of Euler transforms, this is even more important.  An XYZ Euler interpolates well with X rotation, but once you start combining it with Y and Z rotation, you can get some funky, counterintuitive interpolation.  So an Euler bone should be set such that its X axis rotation corresponds with the most likely, most extreme rotation with which it's going to be animated.